1. Field of the Invention
The present invention relates to a fuel ratio control method and a device therefor in a gas turbine combustor comprising a pilot nozzle and a main nozzle, for controlling a fuel ratio of pilot fuel supplied into the pilot nozzle to main fuel supplied into the main nozzle.
2. Description of the Prior Art
In a gas turbine combustor, in order to hold a stable combustion, there is often provided a pilot nozzle for effecting a combustion by two kinds of nozzles of the pilot nozzle and a main nozzle. In the pilot nozzle, a diffusion type combustion is effected wherein pilot flames are held by pilot fuel of about 10% of the entire fuel. The remaining fuel of about 90% is a main fuel supplied into the main nozzle. The main fuel is mixed beforehand with air for a premixed combustion.
In order to reduce NOx amount generated by the combustion, it is preferable to minimize the pilot fuel used for the diffusion type combustion. On the other hand, however, if the pilot fuel is reduced, there occurs a case where NOx amount rather increases by an unstable combustion caused by changes in the combustion state. Because of such circumstances, it is necessary to effect a stable combustion by the minimum pilot fuel. For this purpose, a fuel ratio control of the pilot fuel to the main fuel is extremely important in the gas turbine combustor.
It is therefore an object of the present invention to provide a fuel ratio control method and a device therefor in a gas turbine combustor that is constructed so as to effect a combustion by pilot fuel and main fuel, by which a ratio of pilot fuel supply to main fuel supply is appropriately maintained so as to avoid the unstable combustion, such as combustion vibration or misfire, and to realize a low NOx combustion.
In order to achieve the abovementioned object, the present invention provides the following fuel ratio control method, that is, in a gas turbine combustor being constructed to effect a combustion of pilot fuel and main fuel and being a part of a gas turbine comprising a generator, a fuel ratio control method for controlling a fuel ratio of the pilot fuel to the main fuel, comprising the steps of; setting a fuel ratio control signal corresponding to a generator output LGEN of the generator; and performing a pilot fuel ratio control by correcting the fuel ratio control signal corresponding to a condition change in both or either one of combustion air and fuel supplied into the gas turbine combustor.
In the fuel ratio control method of the above invention, while the fuel ratio control signal is set corresponding to the generator output, this fuel ratio control signal is corrected corresponding to the condition change in both or either one of the combustion air and the fuel. Hence, the fuel ratio control signal according to the present invention becomes such one as accurately corresponds to the generator output on which at least one of the condition changes in the combustion air and the fuel has been well reflected. Thereby, the fuel ratio can be appropriately maintained and a low NOx combustion in the gas turbine combustor can be realized.
Also, in order to achieve the abovementioned object, the present invention provides the following fuel ratio control method, that is, in a gas turbine combustor being constructed to effect a combustion of pilot fuel and main fuel and being a part of a gas turbine comprising a generator, a fuel ratio control method for controlling a fuel ratio of the pilot fuel to the main fuel, comprising the steps of; computing a ratio xcex1 of a generator output LGEN Of the generator to a function F(P2) generated on the basis of a combustor inner air pressure P2, that is, xcex1=LGEN/F(P2); setting a fuel ratio control signal corresponding to the ratio xcex1; and performing a pilot fuel ratio control by correcting the fuel ratio control signal corresponding to a condition change in both or either one of combustion air and fuel supplied into the gas turbine combustor.
In the fuel ratio control method of the above invention, while the fuel ratio control signal is set corresponding to the ratio xcex1=LGEN/F(P2), that is, the ratio xcex1 of the generator output LGEN to the function F(P2) generated on the basis of the combustor inner air pressure P2, this fuel ratio-control signal is corrected corresponding to the condition change in both or either one of the combustion air and the fuel. Hence, the fuel ratio control signal according to the present invention becomes such one as accurately corresponds to the generator output on which at least one of the condition changes in the combustion air and the fuel has been well reflected. Thereby, the fuel ratio can be appropriately maintained and a low NOx combustion in the gas turbine combustor can be realized.
As used in the fuel ratio control method in the gas turbine combustor according to the present invention, the condition change in the combustion air may be at least one of a compressor on-line vane washing signal, an ambient humidity change signal and an ambient pressure change signal. Also, as used in the fuel ratio control method in the gas turbine combustor according to the present invention, the condition change in the fuel may be a fuel component change signal.
Thus, the fuel ratio control signal according to the present invention becomes such one as accurately corresponds to the ratio xcex1=LGEN/F(P2), that is, the ratio xcex1 of the generator output LGEN to the function F(P2) generated on the basis of the combustor inner air pressure P2, on which the compressor on-line vane washing, the ambient humidity change, the ambient pressure change, the fuel component change, etc. have been well reflected.
Also, in order to achieve the abovementioned object, the present invention provides the following fuel ratio control method, that is, in a gas turbine combustor being constructed to effect a combustion of pilot fuel and main fuel and being a part of a gas turbine comprising a generator, a fuel ratio control method for controlling a fuel ratio of the pilot fuel to the main fuel, comprising the steps of; setting a fuel ratio control signal corresponding to a generator output LGEN of the generator; and performing a pilot fuel ratio control by correcting the fuel ratio control signal corresponding to a change rate in the generator output LGEN.
According to the fuel ratio control method of the above invention, the pilot fuel ratio control can be performed based on the pilot fuel ratio control signal that appropriately corresponds to the changes in the generator output on which the change rate in the generator output has been well reflected.
Also, in order to achieve the abovementioned object, the present invention provides the following fuel ratio control method, that is, in a gas turbine combustor being constructed to effect a combustion of pilot fuel and main fuel and being a part of a gas turbine comprising a generator, a fuel ratio control method for controlling a fuel ratio of the pilot fuel to the main fuel, comprising the steps of; computing a ratio xcex1 of a generator output LGEN of the generator to a function F(P2) generated on the basis of a combustor inner air pressure P2, that is, xcex1=LGEN/F(P2); setting a fuel ratio control signal corresponding to the ratio xcex1; and performing a pilot fuel ratio control by correcting the fuel ratio control signal corresponding to a change rate in the generator output LGEN.
According to the fuel ratio control method of the above invention, the fuel ratio control in the gas turbine combustor can be performed by the fuel ratio control signal that accurately corresponds to the ratio xcex1=LGEN/F(P2), that is, the ratio xcex1 of the generator output LGEN to the function F(P2) generated on the basis of the combustor inner air pressure P2, on which the change rate in the generator output has been well reflected.
Furthermore, in order to achieve the abovementioned object, the present invention provides the following fuel ratio control method, that is, in a gas turbine combustor being constructed to effect a combustion of pilot fuel and main fuel and being a part of a gas turbine comprising a generator, a fuel ratio control method for controlling a fuel ratio of the pilot fuel to the main fuel, comprising the steps of; setting a fuel ratio control signal corresponding to a generator output LGEN of the generator, or computing and setting a fuel ratio control signal corresponding to a ratio xcex1 of a generator output LGEN of the generator to a function F(P2) generated on the basis of a combustor inner air pressure P2, that is, xcex1=LGEN/F(P2); and performing a pilot fuel ratio control by correcting the fuel ratio control signal corresponding to a gas turbine deterioration factor.
The gas turbine deterioration factor in this case may be obtained either from the generator output, a fuel flow rate, an ambient pressure, an ambient temperature and a fuel component or from the combustor inner air pressure, an exhaust gas temperature and the generator output.
Thus, according to the present invention, the fuel ratio control in the gas turbine combustor can be appropriately performed by the fuel ratio control signal that accurately corresponds to the generator output LGEN or the ratio xcex1 of the generator output LGEN to the function F(P2) generated on the basis of the combustor inner air pressure P2, on which the gas turbine deterioration factor has been well reflected.
Also, in order to achieve the abovementioned object, the present invention provides the following fuel ratio control device, that is, in a gas turbine combustor being constructed to effect a combustion of pilot fuel and main fuel and being a part of a gas turbine comprising a generator, a fuel ratio control device for controlling a fuel ratio of the pilot fuel to the main fuel, comprising; a computing unit inputted with a generator output LGEN of the generator and a function F(P2) generated on the basis of a combustor inner air pressure P2 for computing a ratio xcex1 thereof, that is, xcex1=LGEN/F(P2); a function setting unit inputted with an output from the computing unit for putting out a fuel ratio control signal; an adder or integrator inputted with at least one of correction signals corrected by a combustion air condition, a fuel condition and a change rate in the generator output LGEN for correcting the fuel ratio control signal; and an adder or integrator inputted with at least one of correction signals corrected by an ambient pressure and a turbine deterioration factor for correcting the output from the computing unit.
According to the fuel ratio control device of the above invention, the fuel ratio control signal is corrected by at least one of the combustion air condition change, the fuel condition change, the generator output change rate and the turbine deterioration factor, and the fuel supply ratio of the pilot fuel to the main fuel is appropriately maintained. Thus, a fuel ratio control in the gas turbine combustor that avoids an unstable combustion, such as combustion vibration, misfire, etc. and effects a low NOx combustion can be realized.